Technical Field
Embodiments of the invention relate generally to magnetic resonance imaging and, more specifically, to an automated control system and method for a superconducting magnet of a magnetic resonance imaging device.
Discussion of Art
Currently, superconducting magnets used in magnetic resonance imagine (MRI) devices installed in clinical sites are typically cooled by a bath of liquid cryogen, such as liquid helium. These magnets require periodic maintenance, which includes ramping up or ramping down (e.g. adjusting current to compensate for annual drift), re-shimming to restore homogeneity, periodic changes of the cryocooler(coldhead), etc. This maintenance is typically performed by a field engineer that must come to the clinical site.
Closed, conductive/convection cooled magnets may require even additional periodic maintenance, which can contribute to increased operating costs and downtime. In particular, such magnets have limited ride-through capability due to the absence of a large helium bath. When the ride-through time limit is exceeded, such as, for example, due to an extended power outage, coldhead failure, or prolonged coldhead changeout, the magnet coils may warm and ultimately quench. After such quench, a field engineer would typically have to come to the clinical site to re-ramp the magnet and re-shim the magnet into optimum operating ranges.
In connection with the above, even though design efforts have been aimed at extending ride-through time, there may always remain certain non-covered clinical scenarios where the maximum duration has been exceed, and the magnet will begin to warm and eventually quench. In these scenarios, the only way to guarantee that the magnet doesn't quench during any outage is to de-energize the magnet before quench occurs, which involves ramping down of the magnet where current is slowly withdrawn from the magnet, and magnetic field strength reduced. Presently, however, ramping up and ramping down is a tedious process, which requires a field engineer to be on site to manually engage the leads and thus close the discharging circuit.
It is therefore desirable to be able to automatically monitor the operational status of the magnet, as well as to remotely control and perform the discharge and ramping up or down of the magnet. In particular, it is desirable to be able to automatically ramp down when an increase in magnet temperature, or other critical parameter is detected above a threshold level, and to automatically re-ramp when any issues are resolved.